The present invention relates to an image forming apparatus for forming an image on a sheet by transferring a color agent of the transfer member to the sheet in accordance with a latent image.
Among conventional image forming apparatuses of this type, are included thermal printers which print by heating a ribbon (transfer member) impregnated with a color agent. Generally, small-sized, low-priced, noise-free, and capable of printing on ordinary paper, these printing machines have recently been used in computers, recorders for the output of word processors, and copying apparatuses.
Generally, in an image forming apparatus of this type, in order to form a color image, a sheet is reciprocated with respect to a head upon forward and reverse rotations of the platen, thereby transferring images having different colors, in several steps. Thereafter, the sheet is discharged onto a discharge tray. In this case, the sheets, each having a multicolor image, are discharged onto a single tray and are sequentially stacked. When two sets of copies are formed with respect to a single original, they are stacked in the same manner as described above. However, when the first three pages of an original are copied as one set and the remaining pages are copied as another set, the copied sheets must be manually sorted, which is a cumbersome operation.